Before being marketed, cosmetic products have to be tested in order to verify their safety. With the object of avoiding the use of animals for such tests, ex vivo methods have been developed.
In particular, Rutherford et al. (British Journal of Dermatology, 91, 503, 1974) have proposed a method for evaluating the irritation undergone by the epidermis after treatment with marginally irritant products, and which consists in determining the presence of acid phosphatase (by the use of p-nitrophenyl phosphate) in the stratum corneum.
Hitherto, such methods could not be used industrially, since they enabled only one product to be tested at a time.